In conventional pumps of the mentioned type, the sickle-shaped filler piece has the tendency to a device for minimizing flutter of a filler piece in "flutter" at certain pressures and/or speed ranges and thus has the tendency to develop noise often identified as being unbearable. The reason for this lies in the radial clearance between the filler piece and the two tooth systems, which clearance permits a back and forth pivoting of the filler piece depending on the pressures just then existing on the internally toothed gear side or on the pinion side. It is known from DE 25 33 646 C2 to design the filler piece in two parts and to press the two parts against the teeth addendum of the internally toothed gear or of the pinion. In the case of pumps running at very high speed (up to 6000 rotations per minute) this solution cannot be applied because of the occurring wear.